The present invention relates to seals between rotatable and stationary components of a turbine and particularly relates to removable seal carriers having abradable seal surfaces for sealing between rotatable and stationary turbine components.
In turbines, particularly steam turbines, seals between rotary and stationary components are a critical part of the steam turbine performance. It will be appreciated that the greater the number and magnitude of steam leakage paths, the greater the losses of efficiency of the steam turbine. For example, labyrinth seal teeth often used to seal between the diaphragms and the rotor or between the rotor bucket tips and the stationary shroud require substantial clearances to be maintained to allow for radial and circumferential movement during transient operations such as startup and shutdown. These clearances are, of course, detrimental to sealing. There are also clearance issues associated with multiple independent seal surfaces, tolerance stack up of radial clearances and assembly of multiple seals, all of which can diminish turbine efficiency. Moreover, it is often difficult to create seals which not only increase the efficiency of the steam turbine but also increase the ability to service and repair various parts of the turbine as well as to create known repeatable boundary conditions for such parts. Accordingly, there is a need for a seal which will eliminate or minimize clearance issues, enable assembly of multiple seals, minimize tolerance stack up of radial clearances, improve serviceability and enable stage by stage adjustment of diaphragms and adjacent seal surfaces effecting improved clearance control.